1. Field of the Invention
The present invention relates to printed radiating antennas. More particularly, the present invention relates to a novel antenna structure comprising two separate wideband notch regions formed on one coplanar substrate.
2. The Prior Art
The use of antennas has become commonplace in electronic devices such as cellular phones, radios, television, and computer networks. An antenna is comprised of a system of wires or other conductors used to transmit or receive radio or other electromagnetic waves.
Many antennas are highly resonant, operating over bandwidths of only a few percent. Such "tuned," narrow-bandwidth antennas may be entirely satisfactory or even desirable for single-frequency or narrowband applications. However, in many situations wider bandwidths are desirable. Such an antenna capable of functioning satisfactorily over a wide range of frequencies is generally referred to as a broadband antenna.
One of the well-known prior art antennas is the exponential notch antenna. The exponential notch takes the form of a substrate such as a circuit board having a conductive surface disposed thereon. An exponential notch is removed from the conductive surface and the antenna is coupled to a 50-.OMEGA. strip line on an opposing surface of the board. This small broadband antenna is well adapted for printed-circuit fabrication.
Another prior art antenna is disclosed in U.S. Pat. No. 4,853,704 issued to Diaz et al. It has a wide bandwidth and one antenna input port. The Diaz et al. antenna comprises a strip conductor, a ground plane separated from and lying parallel to the strip conductor, the grouped plane having a slot therein, the slot extending transverse to the strip conductor, a conductive planar element positioned across the slot and orthogonal to the ground plane, the conductive planar element having curved surfaces extending upwardly and outwardly from the slot. The strip conductor and the ground provided with a slot are generally composed of a dielectric material.
U.S. Pat. No. 5,519,408 issued to Schnetzer discloses a printed tapered notch (coplanar) antenna which has wide bandwidths and one antenna input. The antenna includes a radiating tapered notch and is fed by a section of slotline, which in turn is fed by a coplanar waveguide. The transition from the unbalanced coplanar waveguide to the balanced slotline is accomplished by an infinite balun, where the center conductor of coplanar waveguide terminates on the slotline conductor opposite the ground conductor of the coplanar waveguide. One slot of the coplaner waveguide becomes the feeding slotline for the notch, and the other slot terminates in a slotline open circuit.
U.S. Pat. No. 5,264,860 issued to Quan discloses a flared notch radiator antenna having separate isolated transmit and receive ports. The assembly includes a flared notch radiating element, a transmit port and a receive port, and a signal duplexer is integrated into the assembly for coupling the radiating element to the respective transmit and receive ports. The duplexer provides for coupling the transmit port to the radiating element so that transmit signals are radiated into free space. The duplexer is described as being capable of coupling the radiating element to the receive port so that signals received at the radiating element are coupled to the receive port, and for isolating the transmit port from the receive port. In its preferred embodiment the duplexer is described as a four port circulator, with a first port connected to the transmit port, a second port connected to the balun which couples energy into and out of the flared notch radiator, a third port connected to the receive port, and a fourth port connected to a balanced load. In this manner, the transmit port is isolated from the receive port, and vice versa.
United Kingdom Patent Application No. 2,281,662 issued to Alcatel Espace discloses a printed coplanar notch (single port) with an integrated amplifier. The antenna includes a slot line having an end section with a flared profile to form a Vivaldi antenna. The slot line has an open circuit termination which provides impedance matching so that separate matching circuit is not required between the antenna and an associated low noise amplifier. A series of antennas are disposed in an array to enable localization to be performed by interferometric techniques.
These aforementioned approaches and examples appear to resolve some of the problems associated with transmitting and receiving signals over the broadband frequency range. Additionally, the prior art teaches the use of a plurality of broadband antennas for transmitting and receiving radio frequency energy.
However, none of these inventions teaches a coplanar antenna with two wideband notch radiators operating in a transmit/receive mode which allows separate paths for the transmit and receive antennas so that the transceiver does not require a selection switch.
Accordingly it is an object of the invention to provide a broadband antenna design which is lightweight, simple and compact in design, and inexpensive to manufacture.
Another object of the invention is to provide a single transmit and receive antenna that avoids the need to switch between transmit/receive functions.
It is a further object to provide a broadband antenna having a plurality of geometric configurations to generate an omnidirectional or directional radiation pattern.
Another object of the invention is to provide an antenna that can be used for wireless communication systems.
Other objects, together with the foregoing are attained in the exercise of the invention in the following description and resulting in the embodiments described with respect to the accompanying drawings.